1. Field of the Invention
This invention relates to a mistaken recording inhibiting mechanism for a disc cartridge accommodating a disc capable of re-recording information signals, such as a magneto-optical disc.
2. Description of the Prior Art
The prior art reveals, such as a magnetic disc or a magneto-optical disc, in which information signals once recorded thereon may be erased to permit, recording of new information signals.
The prior art also reveals disc cartridge accommodating a disc of this type which is provided with a mistaken recording inhibiting mechanism for preventing inadvertent erasure of information signals recorded on the disc.
It is possible with the mistaken recording inhibiting mechanism to make a selection between a state permitting re-recording of information signals and a state inhibiting erasure of the information signals already recorded on the disc.
FIG. 1 shows a typical arrangement of a mistaken recording inhibiting mechanism for a disc cartridge which is adapted for making a selection between the re-recordable state and the mistaken recording inhibiting state.
The mistaken recording inhibiting mechanism includes mistaken recording inhibiting member 3 which is movably mounted on a lower half 1 of the cartridge main body for opening or closing a detection hole 2 bored at a corner of the lower half 1.
The mistaken recording inhibiting member 3 is formed by molding synthetic resin. The mistaken recording inhibiting member 3 has a closure web 4 of a size large enough to close the detecting hole 2 bored in the lower half 1 and the first and second resilient arms 5, 6. The first and second resilient arms 5, 6 extend from both ends of the closure web 4 and face each other.
A slide guide 7 for guiding the sliding direction of the mistaken recording inhibiting member 3 is formed upright on the inner surface of the lower half 1. This slide guide 7 is formed substantially parallel to an upright peripheral wall 8 of the lower half 1 constituting the outer wall on the rear side of the cartridge main body.
The surface of the slide guide 7 opposite to the upright peripheral wall 8 is formed with first and second engaging recesses 10, 11 adapted for to engage a retention bead 9 formed on an outer lateral surface of the distal end of one of the resilient arms 5, 6 of the mistaken recording inhibiting member 3. These first and second engaging recesses 10, 11 are formed at such positions that the retention beads 9, 12 may be engaged with the slide guide 7 at positions in which the detecting hole 2 is closed and open, respectively.
The upright peripheral wall 8, formed as part of the lower half 1, has an opening 13 for exposing a retention bead 12 formed on the outer lateral surface of the distal end of the other resilient arm 6 of the mistaken recording inhibiting member 3. This retention bead 112 is accessible from outside of the cartridge main body. The opening 13 long enough to permit the mistaken recording inhibiting member 3 to be moved between a position of closing the detection hole 2 and the position of opening the detection hole 2.
A barrier wall 14 is formed upright within the lower half 1 and faces the opening 13.
Referring to FIG. 2, the mistaken recording inhibiting member 3 is placed within the lower half 1, with the closure web 4 positioned facing the detecting hole 2 and with the resilient arms 5, 7 extending between the slide guide 7 and the upstanding peripheral wall 8.
Meanwhile, a width W.sub.1 between the outer lateral surfaces of the retention beads 9, 12 is selected to be wider than a distance W.sub.2 between the slide guide 7 and the upstanding peripheral wall 8, so that, when the resilient arms 5, 6 are extended between the slide guide 7 and the upstanding peripheral wall 8, the resilient arms 5, 6 are resiliently deflected in a direction towards each other being pressed against the slide guide 7 and the upstanding peripheral wall 8.
The retention bead 12 formed on the other resilient arm 6 of the mistaken recording inhibiting member 3 provided within the lower half 1 is exposed to outside the cartridge main body.
By sliding the retention bead 12 formed on the other resilient arm 6 exposed to outside of the cartridge main body via opening 13, the mistaken recording inhibiting member 3 mounted within the lower half 1 can be moved in a direction shown by an arrow A and an arrow B in FIG. 2, with the resilient arms 5, 6 being guided by the slide guide 7 and the upstanding peripheral wall 8.
When the closure web 4 of the mistaken recording inhibiting member 3 is at the position closing the detecting hole 2, as shown in FIG. 2, the retention bead 9 on the resilient arm 5 is engaged in the first engaging recess 10 for maintaining the detecting hole 2 in the closed state. The mistaken recording inhibiting member 3 can be moved in the direction shown by an arrow A in FIG. 2 until the closure web 4 reaches the position of opening the detecting hole 2, the retention bead 9 is then engaged with the second engaging recess 11, as shown in FIG. 3, for maintaining the detecting hole 2 in the opened state.
Meanwhile, the mistaken recording inhibiting member 3 of the mistaken recording inhibiting mechanism is kept place within the lower half 1 by having the resilient arms 5, 6 resiliently deflected be being pressed against the slide guide 7 and the upstanding peripheral wall 8, so that, unless the width W.sub.1 between the resilient arms 5, 6 is within a certain range, the mistaken recording inhibiting member 3 becomes unable to function properly if the width W.sub.1 between the resilient arms 5, 6 is less than the distance W.sub.2 by too much, then the mistaken recording inhibiting member becomes unable to be supported between the slide guide 7 and the upstanding peripheral wall 8. The result is that the mistaken recording inhibiting member 3 is liable to be detached from the cartridge main body.
On the other hand, if the width W.sub.1 is too much greater than W.sub.2, then the retention bead 9 becomes difficult to engage and disengage from the first and second engaging recesses 10, 11. When This occurs the detecting hole 2 cannot be easily opened or closed reliably and hence the recordable or unrecordable state for information signals cannot be set reliably.
If the mistaken recording inhibiting member 3 is produced by molding synthetic resin, it is difficult to maintain the high dimensional accuracy of the resilient arms 5, 6, necessary to avoid the above-mentioned problems. The resilient arms 5, 6 should extend from one ends of the closure web 4 with a somewhat precise spacing between them, however the resilient arms 5, 6 tend to be deflected towards each other such that the gap between therebetween narrows. This is one of the reasons the above-mentioned problems tends to occur.